This document relates to quality of service (QoS) in communication networks and systems, including wired and wireless communication networks and systems.
Communication networks, wireless or wired, are networks of communication nodes and operate to deliver information or data from one node to another node. Such delivery is frequently accomplished by hoping through one or more intermediate nodes in order to send the information or data from the sending node to the destination node. For a given path from the sending node via one or more intermediate nodes to the destination node, it can be technically challenge to ensure the quality of service (QoS) at the destination node due to various factors that affect the delivery of the information or data. QoS can be characterized by various QoS parameters or metrics. Examples of QoS metrics include the time delays in data transmission, jitters of the arrival times of the data packets, the number of dropped packets, errors in delivered data, and out-of-order delivery. Enhancing QoS and maintaining QoS at a certain desired level are among the major issues in designing and deploying wired and wireless communication networks and various services through such networks.
Wireless communication systems use a network of base stations to communicate with wireless devices registered for services in the systems. The base stations, which conceptually locate at the center of respective cells of wireless radio coverage, transmit information to respective mobile stations (MSs) registered in the network, which are also referred to as subscriber stations (SSs), via respective downlink (DL) radio signals sent out from the base stations. The mobile stations transmit information to their serving base stations via uplink (UL) radio signals. Each base station emits radio signals that carry data such as voice data and other data content to wireless devices. Such a signal from a base station can include overhead load for various communication management functions, including information to allow a wireless device to identify a cell sector of a base station, to synchronize signaling in time and frequency. Each wireless device processes such information in the overhead load of each received signal prior to processing of the data. OFDM and OFDMA systems are examples of wireless communications and are based on orthogonality of frequencies of multiple subcarriers to achieve a number of technical advantages for wideband wireless communications, such as resistance to multipath fading and interference.
The radio coverage of a wireless network of fixed base stations may be limited due to various factors. Certain structures in an intended service area may block the radio signals of one or more base stations. For example, a tall building may shield a particular area from the radio signal from a base station, thus creating an undesired shadowing. At the edge of a radio cell, the signal strength can be weak and hence can increase the error rate in the wireless communications. One approach to mitigating these and other limitations is to increase the number of base stations in a given service area. In one implementation under this approach, one or more relay stations (RSs) can be deployed among certain fixed base stations to relay communication signals between a subscriber station and a base station, thus extending the coverage and improving the communication capacity and quality of the base station. A relay station may be a fixed transceiver or a mobile transceiver station depending on the specific conditions for deploying such as relay station. A subscriber station signal may hop through one or more RSs before reaching a serving base station. Multi-hop Relay (MR) modes can be provided to use relay stations for enhanced coverage and service to subscribers. For example, a multi-hop relay wireless network under IEEE 802.16j includes MR base stations (MR-BSs) and relay stations (RSs).
Effective QoS mechanisms are desirable in such multi-hop relay networks and other multi-hop networks to provide high quality delivery of data and services to subscribers.